To conserve nickel and reduce costs, a number of procedures have been adopted by the nickel plating industry. Some of these procedures include reducing the thickness of the nickel deposited, substituting cobalt for some or all of the nickel when cobalt is less expensive or more readily available, and more recently electrodepositing nickel-iron, cobalt-iron, or nickel-cobalt-iron alloys in which as much as 60% of the deposit may consist of relatively inexpensive iron.
However, when deposit thickness is reduced, it is necessary to use more effective or "powerful" nickel brighteners or higher concentrations of nickel brighteners, so that the degree of brightening and leveling to which the nickel plating industry has grown accustomed may be obtained. The more "powerful" nickel brighteners or high concentrations of brighteners, while capable of producing the desired brightening and leveling, may nevertheless cause unacceptable side effects. The deposits may peel or may be highly stressed, severely embrittled, less receptive to subsequent chromium deposits or exhibit hazes, reduced low current density covering power or "throw" or striations and skip plate i.e.; areas in which a deposit is not obtained.
In order to overcome the deleterious effects of "powerful" brighteners or high concentrations of brighteners, the addition of various sulfinic acids or their salts has been recommended by Brown in U.S. Pat. No. 2,654,703; the use of organic hydroxy sulfonates has also been recommended by Passal in U.S. Pat. No. 3,697,391 for this purpose.
Unfortunately these compounds severely reduce the deposit leveling and bright range.
Further attempts have been made to improve low current density characteristics when "powerful" brighteners or high concentrations of brighteners are used:
(i) The use of aromatic monoamines, aromatic polyamines, unsubstituted polyethylenepolyamine by Du Rose in U.S. Pat. No. 3,630,857. PA1 (ii) The use of N-(3-sulfopropyl) pyridinium inner salts by Rosenberg in U.S. Pat. No. 3,862,019. PA1 (iii) The use of N-disubstituted amino propyne or its hydrochloride by Law in U.S. Pat. No. 4,054,495.
While these compounds do improve low current density characteristics, they still do not produce low current density deposits which are free from darkness and skip plate.
It is an object of this invention to provide processes and compositions for depositing electrodeposits of nickel which possess a greater tolerance for "powerful" brighteners and high concentrations of brighteners. It is also an object of this invention to accomplish this tolerance without affecting the leveling of the deposits. It is further an object of this invention to accomplish this tolerance while providing low current areas free from darkness and skip plate without affecting the bright range.